The Polymerase Chain Reaction (PCR) is used to amplify DNA in vitro. Each cycle consists of three steps in a specific thermal sequence:
• Denaturation: Heating the target DNA to approximately $94^\circ\text{C}$ to separate the double-stranded DNA into single strands.
• Annealing: Lowering the temperature to allow primers to bind to their complementary sequences on the single-stranded DNA.
• Extension: The temperature is adjusted (usually to $72^\circ\text{C}$) to allow *Taq* polymerase to synthesize new DNA strands starting from the primers.